Thanks everyone.
Yes it does adjust by unbolting the right hand frame from the base plate. I've only set it up so it do my front and rear wheels but could easily drill another set of holes in the base to cope with any axle length.
The ruler on the steel angle channels acts as the dishing measurement but as I get into this I could make one of those angled jobbies I've seen for the dish. I'll see how I go 'as built' for now.
Just need to get into the witchcraft that is wheel truing now. I did have a go with the wheel on the bike and made things worse hence making the stand where I can properly see what is going on and more importantly be comfortable doing so.